Aluminum Alloy Furnace

Release time:

Jun 15,2026

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Aluminum Alloy Furnace Charge Materials and Return Scrap Management

Furnace Charge Materials for Aluminum Alloys

1. What Furnace Charge Materials Are Used for Aluminum Alloys?

The furnace charge materials used for preparing aluminum alloys can be divided into three main categories:

Pure metals, called new material or primary metal
Return scrap or recycled charge from the plant
Master alloys

The pure metals used in aluminum alloy production are mainly pure aluminum and various alloying elements added in pure-metal form. Pure aluminum charged into the furnace may be either solid or liquid.

In electrolytic aluminum plants, or in aluminum processing plants using molten primary aluminum, liquid charge is mainly used. Alloying elements such as low-melting-point and easily fusible metals including copper, manganese, nickel, iron, silicon, chromium, titanium, zinc and beryllium are often crushed into small pieces before charging, so that they can be batched more easily and dissolve more quickly in molten aluminum.

Scrap sources include both in-house scrap and purchased scrap. In-house scrap comes from process scrap and geometric scrap generated in melting and processing workshops. The yield of aluminum processing plants is generally 60%-75%, which means that 25%-40% of raw materials become scrap. This part of scrap is one of the important raw material sources. Purchased scrap comes from material users.

Some alloying elements with high melting points or slow dissolution rates in molten aluminum are usually first made into master alloys and then added quantitatively according to the required composition of the finished alloy. These include master alloys of copper, manganese, nickel, iron, silicon, chromium, titanium, beryllium and other elements.

In aluminum processing plants, to obtain good product quality, the more primary aluminum used, the better. To reduce production cost, a large amount of scrap aluminum is often used. To ensure product quality, the amount of primary aluminum used is usually preferably not less than 50%.

In electrolytic aluminum plants, the price difference of raw materials is not the main issue. The general principle should be to make full use of the residual heat of molten primary aluminum at normal temperature, use as much molten primary aluminum as possible, and ensure product quality.

Formula for Charge Calculation

The formula for charge calculation is:

W = A × [[(t - 0.001) / 100] × (21.64 / 47.90)
      + [(v - 0.002) / 100] × (21.64 / 50.95)] × [1.5 + (b / 100)]

After rearrangement:

W = [1.5 × (A / b)] × [(t - 0.001) × (21.64 / 47.90)
    + (v - 0.002) × (21.64 / 50.95)]

2. How Should Return Scrap Be Managed?

In independent electrolytic aluminum plants, the amount of in-house production scrap is very small.

When electrolytic aluminum production and aluminum processing production are optimally combined, a large amount of production scrap will exist. Scrap can be divided into in-house scrap and purchased scrap.

According to the GB/T 13586-1992 standard for aluminum and aluminum alloy scrap classification and technical conditions, scrap can be divided into three categories according to physical form:

Lump scrap
Chip scrap
Slag and ash scrap

Each type of scrap can also be divided into four major groups according to chemical composition:

Pure aluminum
Wrought aluminum alloy
Cast aluminum alloy
Mixed aluminum and aluminum alloy

Each major group can then be subdivided into several subgroups according to chemical composition differences. Scrap in each group is further divided into six grades according to alloy designation, mixed impurities and surface corrosion condition.

Mixed charge is divided into three grades according to aluminum content. Slag and ash are divided into five grades according to aluminum content. Each enterprise should establish reasonable scrap classification and grading standards according to the actual source of its own scrap.

Generally, scrap may be graded according to the following principles:

Grade 1 scrap: clear chemical composition, relatively large size, clean and compact, and can be directly charged into the furnace to produce finished alloy.
Grade 2 scrap: clear chemical composition, smaller size, slightly contaminated, and can be directly charged into the furnace to produce finished alloy.
Grade 3 scrap: clear chemical composition, but poor compactness and serious contamination; it can be used for finished alloy only after remelting treatment.
Grade 4 scrap: mixed charge.
Grade 5 scrap: slag and furnace ash.

During production, the amount of Grade 5 scrap should be reduced as much as possible, and the generation of Grade 4 scrap should be avoided as much as possible.

Return Scrap Storage and Use

To ensure the quality of finished alloys, accurate batching is extremely important. To accurately prepare the chemical composition of finished alloys, the plant’s scrap must be classified, graded, stored and used according to the actual situation of the plant.

Even for aluminum alloys of the same designation, different products have different requirements for impurity content. When the amount of scrap is large, it should also be stored and used according to product category.

For example, for 3A21 aluminum alloy, when producing soft sheet, the iron content should be controlled at 0.45%-0.60%, and the silicon content should be controlled below 0.40%. When producing semi-hard sheet, the iron content should be controlled below 0.25%, and the silicon content should be controlled below 0.20%.

Large pieces of high-quality scrap can be directly returned to the furnace to prepare finished alloys of the same type. Poor-quality chips, which are Grade 3 scrap, are allowed to be used in limited quantities for finished alloy production only after remelting treatment.

Purchased scrap from users can also be treated in the same way. Storage must be classified, graded and separated, and scrap must never be mixed.

In general, purchased scrap has mixed composition and poor quality, so it is not suitable for direct use.

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